In semiconductor device fabrication, various layers of insulating material, semiconducting material and conducting material are patterned to create features that form semiconductor components, such as transistors, capacitors and resistors. These semiconductor components are interconnected to achieve their intended function, thereby forming an integrated circuit (IC) device. The IC device (chip) will additionally include bond pads for forming interconnections with external packaging components; for example, a printed circuit board through wire bonding or flip-chip bonding. Bond pads are typically made from a conductive material, such as aluminum (Al) or copper (Cu).
After fabrication of the IC devices is completed, passivation layers are formed on the IC devices to protect chip surfaces from mechanical damage and to prevent moisture build-up and penetration into the IC devices. Moisture penetration into IC devices may cause adverse effects that include, but not limited to, corrosion, reduction of bulk resistivity and electrical polarization effects. The passivation layers have openings over the bond pads for the bonding wires or solder bumps to be subsequently connected.
One of the challenges in forming the bond pad openings in the passivation layer is fluorine contamination from etch chemicals used in the plasma etching process. The plasma etching process is typically performed in a fluorine-containing gases environment; for example, hydrofluorocarbon (CHF3). Residual fluorine may remain predominantly on end portions of the passivation layer at the bond pad openings as adhesive-like contaminants, i.e., fluorine polymers.
The issue of fluorine contamination is particularly challenging for Al bond pads, because, over time (e.g., a period of storage of IC devices), the fluorine polymers may discharge fluorine contaminants, which will corrode the bond pad surfaces and/or form fluorinated Al crystallites on the bond pad surfaces. As a result, IC devices may exhibit higher failure rate or performance degradation due to reduced adhesion of the bonding wires or solder bumps to the bond pad surface.